Bubbly structures in a cavitating slot orifice

Perpar, M.; Polutnik, E.; Pecar, M.; Žun, Iztok

doi:10.1016/j.expthermflusci.2013.11.003

Cited by 8 publications

(1 citation statement)

References 17 publications

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“…Such greyscale intensity based techniques may not always be appropriate to other regimes such as dispersed flows or annular flows. Nevertheless, various studies exist where the above pixel counting and/or greyscale intensity based techniques have been employed to determine void fractions, in flow regimes where it may not be perfectly applicable [10][11][12][13][14][15][16][17][18]. In the above cases, the flow characteristics are often assumed to be two-dimensional (2D) or the void fractions are estimated from instantaneous images.…”

Section: Introductionmentioning

confidence: 99%

Direct comparison of shadowgraphy and x-ray imaging for void fraction determination

Dash

Jahangir

Poelma

2018

Meas. Sci. Technol.

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A quantitative analysis of two imaging modalities, shadowgraphy and x-ray imaging, is presented in the framework of void fraction determination. The need for this arises from the fact that shadowgraphs are sometimes utilized to quantify void fraction profiles, which is an unproven method. Time-averaged x-ray images are used to evaluate the performance of the time-averaged shadowgraphs. The case of a cavitating flow through an axisymmetric converging-diverging nozzle (‘venturi’) is considered, for three separate cavitation numbers. The complex nature of the cavitating flow through the venturi manifests itself in the occurrence of three distinct regimes: a swarm of tiny bubbles; a large, coalesced cavity near the wall; and a drifting/collapsing cavity. The flow regime governs the performance of shadowgraphy for void fraction determination, with two of the three regimes deemed acceptable for shadowgraphy. The quantitative comparison exemplifies that sole reliance on shadowgraphy may lead one to draw improper conclusions on the void fraction distributions, even at a qualitative level.

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